Mark IV and Bogner cab Impedance Mismatch

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peckhart

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I don't like that I have to run the Mark IV on 8ohm into a 16ohm cab.
Trying to weigh some options. Thought about a new OT for the amp with a 16ohm tap, but then thought if I am sinking $ into this maybe 8ohm speakers in the Bogner cab is a better long term investment.
I like the V30s in it just fine, but do recall loving the V30 and G12H30 mix I had in a cab a while ago.
Started looking at their WGS equivalents, but then started wondering if I'd be taking a step back.

Thoughts?
 
I think my MKIV has a 16 ohm out....? :confused:

I know they have different MKIV's. Must not have the same features. I know placements of options vary.

I think it's safe to run them mismatched. Someone will confirm.
 
Have you compared the tone of a similar 8 ohm cabinet to know what the difference might be? It's possible that it wouldn't sound any different (or better) and you could be spending money for no reason... :dunno:
 
It's definitely safe to run the MKIV like that. No issues. I personally like the sound from the 16 Ohm out of an amp more myself... I also prefer the sound of 16 Ohm speakers. But you're fine doing it as is.
 
You could rewire cab to 4ohms and use the 4ohm tap....
 
There is no Simulclass transformer with a 16 ohm output. Other than running the mismatch you can add a other 4x12 so the total is 8 ohms.... or rewire the cab to 4 ohms as mentioned.
 
Can you rewire the cab for 4 ohms and have a 4 ohm option on the amp? Thats the cheapest route
 
It's perfectly safe to run that way from my understanding..low (from amp) to high (cab) is safe. So you could run 4-16 or 8-16. The other way around is dangerous to your tubes and transformers.
 
Running any impedance mismatch is certainly not optimal for tone, and definitely carries some risk. In the configuration you're using ( a load impedance higher than the amp ), the danger is flyback voltage damaging the tubes and OPT. However, for this to occur, you would have to be running the power section pretty close to flat out. If you are using the amp at reasonable master vol settings and like the sound, and given that the impedance mismatch is only 1 step, you're likely fine.

Simplest and cheapest solution is to re-wire the cab to 4 ohms, see what you think of the tone change, and go from there.
 
It's works fine, and sounds fine. What are you hoping to accomplish? Seems like a lot of money and time invested in swapping.
 
Racerxrated":1icnaz6g said:
It's perfectly safe to run that way from my understanding..low (from amp) to high (cab) is safe. So you could run 4-16 or 8-16. The other way around is dangerous to your tubes and transformers.
Click to expand...
As I stated above, 8 into 16 ohms is usually OK, but I would personally NEVER run 4 into 16 ohms. Risk of flyback is increased considerably. It ain't worth it.
And yes, a mismatch down ( cab lower than the amp) is a definite no-no.
 
Rewire a 16 ohm 4x12 to 4ohms is easy. The most difficult part is removing the 15 screws on the back of the amp.
Personally I feel the IV sounds best running at 4ohms. The only issue is you can not run two 4ohm cabs (2ohm load). So if you ever want to run two cabs I would just leave the mismatch.

Some people prefer the sound of a mismatch. My 4x12 cabs are all wired 16ohm or have a switch to change between 4 and 16 ohms.
 
Generally speaking, running like that should deaden the tone dull the top end. At least that's my experience. So if that's the issue then several paths mentioned above. If it sounds fine then you're good.

FWIW, I'd be more inclined to make the cab 8 ohms. Or...better yet...just get a used Mesa Traditional 4x12 with original 8ohm V30s for like $400 or whatever. With the money you might throw at it...you could just have another cab.
 
Thanks for all the comments guys.
My concern is the flyback as explained by fusedbrain. I had always heard that as long as the load is higher than the amp expects you are ok, but started reading some different things recently that suggest otherwise. Just makes me nervous.
I don't think I am pushing the amp terribly hard. The Mark IV is one that gets loud super fast. Channel volumes on 3 and going to 2 on the master is pumping plenty of volume with a loud drummer. I am assuming it has a lot more on tap, but maybe the dial numbers are misleading.
I am happy with the way the cab sounds right now. I get good tones with the Mark IV into it and also play the Helios into it.

Should I expect it to sound different if I rewired to 4ohm? I see now that if I put all 4 in parallel I will get 4ohm, which both of my amps have taps for.
 
Yes it will sound different if change the cab from 16 to 4 ohm wiring. It's also going to change the feel.
 
If you can add a 4/16 switcher that might be the best. I got a tech to add it on one of my cabs.
 
SpiderWars":2plexmld said:
Generally speaking, running like that should deaden the tone dull the top end. At least that's my experience. So if that's the issue then several paths mentioned above. If it sounds fine then you're good.

FWIW, I'd be more inclined to make the cab 8 ohms. Or...better yet...just get a used Mesa Traditional 4x12 with original 8ohm V30s for like $400 or whatever. With the money you might throw at it...you could just have another cab.
Click to expand...
The mesa cab thought has crossed my mind. Problem is finding one local, plus then I have 3 4x12s. Do I really need 3 ?
 
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